Silicone, polysulfide and polyether synthetic rubbers vulcanizable at room temperature are used as dental impression materials, mold materials for general uses and sealing materials. As any of these synthetic rubbers, however, have relatively high production costs and are obtained by complex reactions, there are problems of operation and quality control. Further, since these synthetic rubbers are obtained by use of irreversible reactions, if once these are used, these can not be reused and must be wasted. Namely, there are problems in the aspect of costs and effective uses of resources.
As materials for solving these problems, the so-called thermoplastic elastomers have been noticed. The thermoplastic elastomers have a general term of high-molecular weight materials which show rubber elasticity at room temperature and easily give plasticity and moldability at high temperature. In the molecular structures, the elastomers are copolymers in which hard segments and soft segments combine. Thermoplastic elastomers by combinations of various hard segments and soft segments including polystyrene-polybutadiene copolymer have already existed as known compounds. However, any of them has relatively high modulus or high softening temperature which renders them unsuited to use as mold materials for general uses and sealing materials including dental impression materials.
Thermoplastic elastomers which are suitable for uses of dental impression materials, mold materials for general uses and sealing materials should have good rubber elasticity at room temperature, furthermore softening temperature of about 50.degree. C. and Young's modulus of about 2 MPa and under.